One of the things that makes art history so interesting to me is that it has always seemed to be in a state of flux. Some call it shifting sands, others see it as a regular, rhythmic swinging of a pendulum, others as something on the order of rocking the boat. Whatever the case there is movement, back and forth, often from one extreme to another. In early periods some of these shifts came over a period of a hundred years or so as in the development of the High Renaissance out of the Early Renaissance, and that from medieval painting, etc. As time has progressed, the swings in taste and style have become more and more generational. That is sons rejecting out of hand that which their fathers did, simply because their fathers did it.
As an example, Neo Classicism in the early 1700's sprang from the excesses of the Baroque. A generation later comes Rococo, light as air and about as filling as cotton candy--pretty but shallow. Romanticism kept the decadence of the Rococo while breathing new excitement into the staid lines of Neo-Classical artists like David and Ingres. This in turn led to a stratified, etched in stone codification of art into an official, academic style to which the Impressionist so fiercely rebelled. And then, the Post-Impressionists struggled to return painting to something more earthy and solid, if somewhat esoteric as well. And once the disintegration of form began, there was no stopping it until content also largely disappeared.

And in this century, where once these swings took at least a generation, movements rose and fell in a decade, often less as the pace of life and change picked up, dragging with it the pace of change in art as well. Inevitably, if change begins to happen rapidly enough the swings back and forth become so rapid that they can no longer be seen, like wiper blades on an exceedingly rainy night. The effect is to stabilise art rather than move it in different directions. And that, I think is what we are coming to see today. Movements, like those of the past, are passť. There are simply too many of them to make any of them significant. But without movement there is no momentum and without momentum, no real excitement. The result is ennui.